If you have gas heating but with an electric element in it......
Then buy a whole new tank...get a plumber to fit it....and a new element along with it
The latest tanks have double coils inside for the hot water and the speed it heats...particularly when a new boiler joins it... Now or future....is impressive.
I had mine changed several years ago....and had the boiler changed two years later
The sheer volume of chalk in the tank was unreal